Method of making a bimetallic catalyst with higher activity

ABSTRACT

Methods of preparing bimetallic catalysts are disclosed. The methods include the steps of providing a supported non-metallocene catalyst, contacting a slurry of the supported non-metallocene catalyst in a non-polar hydrocarbon with a solution of a metallocene compound and an alumoxane, and drying the contact product to obtain a supported bimetallic catalyst. The supported non-metallocene catalyst is prepared by dehydrating a particulate support material at a temperature of greater than 600° C., preparing a slurry of the dehydrated support in a non-polar hydrocarbon, contacting the slurry with an organomagnesium compound and an alcohol, contacting the resulting slurry with a non-metallocene compound of a Group 4 or Group 5 transition metal, and drying the contact product to obtain a supported non-metallocene catalyst as a free-flowing powder. The bimetallic catalysts show increased activity relative to catalysts prepared using support materials dehydrated at lower temperatures.

This application claims the benefit of Provisional Application No.60/334,576, filed Nov. 30, 2001.

1. FIELD OF THE INVENTION

The invention relates generally to methods of producing bimetalliccatalysts for olefin polymerization reactions. In particular, theinvention provides methods of making supported bimetallic catalystsincluding a non-metallocene transition metal catalyst and a metallocenecatalyst, the methods providing bimetallic catalysts having improvedactivity. The catalysts are particularly useful in polymerizingpolyolefins to form polyolefin resins with bimodal molecular weightdistribution (MWD) and/or bimodal composition distribution, in a singlereactor.

2. BACKGROUND

Polyolefin resins having bimodal molecular weight distributions and/orbimodal composition distributions are desirable in a number ofapplications. Resins including a mixture of a relatively highermolecular weight polyolefin and a relatively lower molecular weightpolyolefin can be produced to take advantage of the increased strengthproperties of higher molecular weight resins and articles and films madetherefrom, and the better processing characteristics of lower molecularweight resins.

Bimetallic catalysts such as those disclosed in U.S. Pat. Nos. 5,032,562and 5,525,678, and European Patent EP 0 729 387, can produce bimodalpolyolefin resins in a single reactor. These catalysts typically includea non-metallocene catalyst component and a metallocene catalystcomponent which produce polyolefins having different average molecularweights. U.S. Pat. No. 5,525,678, for example, discloses a bimetalliccatalyst in one embodiment including a titanium non-metallocenecomponent which produces a higher molecular weight resin, and azirconium metallocene component which produces a lower molecular weightresin. Controlling the relative amounts of each catalyst in a reactor,or the relative reactivities of the different catalysts, allows controlof the bimodal product resin. Other background references include EP 0676 418, WO 98/49209, WO 97/35891, and U.S. Pat. No. 5,183,867.

Methods of producing bimetallic catalysts are disclosed in thereferences cited above. These methods generally include depositing anon-metallocene transition metal compound on a dehydrated poroussupport, and subsequently depositing a metallocene compound on the samesupport. For some applications, however, the activity of the knownbimetallic catalysts is undesirably low. It would be desirable to havemethods of producing bimetallic catalysts for producing bimodalpolyolefin resins, which have a higher activity than bimetalliccatalysts currently known.

3. SUMMARY OF THE INVENTION

It has been surprisingly found that both supported non-metallocenetransition metal catalysts and supported bimetallic catalysts preparedusing a support dehydrated at a temperature of greater than 600° C.shows increased activity relative to the corresponding conventionalcatalysts.

In one embodiment, the present invention provides a method of producinga bimetallic catalyst, including the steps of providing a supportednon-metallocene catalyst, contacting a slurry of the supportednon-metallocene catalyst in a non-polar hydrocarbon with a solution of ametallocene compound and an alumoxane, and drying the contact product toobtain a supported bimetallic catalyst. The supported non-metallocenecatalyst is prepared by dehydrating a particulate support material at atemperature of greater than 600° C., preparing a slurry of thedehydrated support in a non-polar aliphatic hydrocarbon, contacting theslurry with an organomagnesium compound and an alcohol, contacting theresulting slurry with a non-metallocene compound of a Group 4 or Group 5transition metal, and drying the contact product to obtain a supportednon-metallocene catalyst as a free-flowing powder.

In another embodiment, the present invention provides a method ofproducing a bimetallic titanium/zirconium catalyst, including the stepsof providing a supported non-metallocene titanium catalyst, contacting aslurry of the titanium catalyst in a non-polar aliphatic hydrocarbonwith a solution of a zirconium metallocene compound and methylalumoxane,and drying the contact product to obtain a supported bimetalliccatalyst. The supported titanium catalyst is prepared by dehydratingsilica at a temperature of greater than 600° C., preparing a slurry ofthe dehydrated silica in a non-polar hydrocarbon, contacting the slurryin turn with dibutylmagnesium, n-butanol, and a titanium compound, anddrying the contact product to obtain a supported non-metallocenetitanium catalyst as a free-flowing powder.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the average activity versus silica dehydration temperaturefor a supported non-metallocene transition metal catalyst and asupported bimetallic catalyst.

5. DETAILED DESCRIPTION

In one aspect, the invention provides processes for preparing abimetallic catalyst composition. The process includes providing asupported non-metallocene catalyst, contacting a slurry of the supportednon-metallocene catalyst in a non-polar hydrocarbon with a solution of ametallocene compound and an alumoxane in an aromatic solvent, and dryingthe contact product to obtain a supported bimetallic catalystcomposition. It has been surprisingly found that both supportednon-metallocene transition metal catalysts and supported bimetalliccatalysts prepared using a support dehydrated at a temperature ofgreater than 600° C. show increased activity relative to thecorresponding conventional catalysts.

5.1 Supported Non-Metallocene Catalyst

In one step, the method includes providing a supported non-metallocenecatalyst. The supported non-metallocene catalyst is prepared bydehydrating a particulate support, and contacting a slurry of thedehydrated support in a non-polar hydrocarbon solvent in turn with anorganomagnesium compound, an alcohol, and a non-metallocene transitionmetal compound. Solvents are removed from the product to yield asupported non-metallocene catalyst. The catalyst synthesis is carriedout in the absence of water and oxygen.

The support is a solid, particulate, porous, preferably inorganicmaterial, such as an oxide of silicon and/or of aluminum. The supportmaterial is used in the form of a dry powder having an average particlesize of from about 1–500 μm, typically from about 10–250 μm. The surfacearea of the support is at least about 3 m²/g, and typically much larger,such as 50–600 m²/g or more. Various grades of silica and aluminasupport materials are widely available from numerous commercial sources.

In a particular embodiment, the carrier is silica. A suitable silica isa high surface area, amorphous silica, such as a material marketed underthe tradenames of Davison 952 or Davison 955 by the Davison ChemicalDivision of W.R. Grace and Company. These silicas are in the form ofspherical particles obtained by a spray-drying process, and have asurface area of about 300 m²/g, and a pore volume of about 1.65 cm³/g.It is well known to dehydrate silica by fluidizing it with nitrogen andheating at about 600° C., such as described, for example, in U.S. Pat.No. 5,525,678. It has been surprisingly found, however, that theactivity of supported catalysts such as the bimetallic catalystsdescribed herein is unexpectedly sensitive to the dehydrationtemperature. Thus, whereas the examples of U.S. Pat. No. 5,525,678, forexample, show dehydration at 600° C., the present inventors havesurprisingly found that much higher catalyst activity can be achievedwhen dehydration temperatures of greater than 600° C. are used in thecatalyst support preparation. The silica can be dehydrated at greaterthan 600° C., or at least 650° C., or at least 700° C., or at least 750°C., up to 900° C. or up to 850° C. or up to 800° C., with ranges fromany lower temperature to any upper temperature being contemplated. Asshown in the Examples herein, the activity of silica supportedbimetallic catalysts increases non-linearly with silica dehydrationtemperature up to a maximum at about 700–850° C. or 750–800° C., andthese ranges of maximum catalyst activity are particularly preferred.

The dehydrated silica is slurried in a non-polar hydrocarbon. The slurrycan be prepared by combining the dehydrated silica and the hydrocarbon,while stirring, and heating the mixture. To avoid deactivating thecatalyst subsequently added, this and other steps of the catalystpreparation should be carried out at temperatures below 90° C. Typicaltemperature ranges for preparing the slurry are 25 to 70° C., or 40 to60° C.

Suitable non-polar hydrocarbons for the silica slurry are liquid atreaction temperatures, and are chosen so that the organomagnesiumcompound, alcohol and transition metal compound described below are atleast partially soluble in the non-polar hydrocarbon. Suitable non-polarhydrocarbons include C₄–C₁₀ linear or branched alkanes, cycloalkanes andaromatics. The non-polar hydrocarbon can be, for example, an alkane,such as isopentane, hexane, isohexane, n-heptane, octane, nonane, ordecane, a cycloalkane, such as cyclohexane, or an aromatic, such asbenzene, toluene or ethylbenzene. Mixtures of non-polar hydrocarbons canalso be used. Prior to use, the non-polar hydrocarbon can be purified,such as by percolation through alumina, silica gel and/or molecularsieves, to remove traces of water, oxygen, polar compounds, and othermaterials capable of adversely affecting catalyst activity.

The slurry is then contacted with an organomagnesium compound. Theorganomagnesium compound is a compound of RMgR′, where R and R′ are thesame or different C₂–C₁₂ alkyl groups, or C₄–C₁₀ alkyl groups, or C₄–C₈alkyl groups. In a particular embodiment, the organomagnesium compoundis dibutyl magnesium.

The amount of organomagnesium compound used is preferably not more thanthe amount of the organomagnesium compound to the silica slurry thatwill be deposited, physically or chemically, onto the support, since anyexcess organomagnesium compound may cause undesirable side reactions.The support dehydration temperature affects the number of hydroxyl siteson the support available for the organomagnesium compound: the higherthe dehydration temperature the lower the number of sites. Thus, theexact molar ratio of the organomagnesium compound to the hydroxyl groupswill vary and can be determined on a case-by-case basis to assure thatlittle or no excess organomagnesium compound is used. The appropriateamount of organomagnesium compound can be determined readily by oneskilled in the art in any conventional manner, such as by adding theorganomagnesium compound to the slurry while stirring the slurry, untilthe organomagnesium compound is detected in the solvent. As anapproximate guide, the amount of the organomagnesium compound added tothe slurry is such that the molar ratio of Mg to the hydroxyl groups(OH) on the support is from 0.5:1 to 4:1, or 0.8:1 to 3:1, or 0.9:1 to2:1, or about 1:1. The organomagnesium compound dissolves in thenon-polar hydrocarbon to form a solution from which the organomagnesiumcompound is deposited onto the carrier. The amount of theorganomagnesium compound (moles) based on the amount of dehydratedsilica (grams) is typically 0.2 mmol/g to 2 mmol/g, or 0.4 mmol/g to 1.5mmol/g, or 0.6 mmol/g to 1.0 mmol/g, or 0.7 mmol/g to 0.9 mmol/g.

It is also possible, but not preferred, to add the organomagnesiumcompound in excess of the amount deposited onto the support and thenremove it, for example, by filtration and washing.

Optionally, the organomagnesium compound-treated slurry is contactedwith an electron donor, such as tetraethylorthosilicate (TEOS) or anorganic alcohol R″OH, where R″ is a C₁–C₁₂ alkyl group, or a C₁ to C₈alkyl group, or a C₂ to C₄ alkyl group. In a particular embodiment, R″OHis n-butanol. The amount of alcohol used is an amount effective toprovide an R″OH:Mg mol/mol ratio of from 0.2 to 1.5, or from 0.4 to 1.2,or from 0.6 to 1.1, or from 0.9 to 1.0.

The organomagnesium and alcohol-treated slurry is contacted with anon-metallocene transition metal compound. Suitable non-metallocenetransition metal compounds are compounds of Group 4 or 5 metals that aresoluble in the non-polar hydrocarbon used to form the silica slurry.Suitable non-metallocene transition metal compounds include, forexample, titanium and vanadium halides, oxyhalides or alkoxyhalides,such as titanium tetrachloride (TiCl₄), vanadium tetrachloride (VCl₄)and vanadium oxytrichloride (VOCl₃), and titanium and vanadiumalkoxides, wherein the alkoxide moiety has a branched or unbranchedalkyl group of 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms.Mixtures of such transition metal compounds may also be used. The amountof non-metallocene transition metal compound used is sufficient to givea transition metal to magnesium mol/mol ratio of from 0.3 to 1.5, orfrom 0.5 to 0.8.

The solvent is removed in a conventional manner, such as by evaporationor filtering, to obtain the dry, supported non-metallocene transitionmetal catalyst.

5.2 Supported Bimetallic Catalyst

The supported bimetallic catalyst is prepared by depositing ametallocene compound onto the supported non-metallocene transition metalcatalyst.

The term “metallocene compound” as used herein means compounds having aGroup 4, 5 or 6 transition metal (M), with a cyclopentadienyl (Cp)ligand or ligands which may be substituted, at least onenon-cyclopentadienyl-derived ligand (X), and zero or oneheteroatom-containing ligand (Y), the ligands being coordinated to M andcorresponding in number to the valence thereof. The metallocene catalystprecursors generally require activation with a suitable co-catalyst(referred to as an “activator”), in order to yield an active metallocenecatalyst, i.e., an organometallic complex with a vacant coordinationsite that can coordinate, insert, and polymerize olefins. Themetallocene compound is a compound of one or both of the followingtypes:

(1) Cyclopentadienyl (Cp) complexes which have two Cp ring systems forligands. The Cp ligands form a sandwich complex with the metal and canbe free to rotate (unbridged) or locked into a rigid configurationthrough a bridging group. The Cp ring ligands can be like or unlike,unsubstituted, substituted, or a derivative thereof, such as aheterocyclic ring system which may be substituted, and the substitutionscan be fused to form other saturated or unsaturated rings systems suchas tetrahydroindenyl, indenyl, or fluorenyl ring systems. Thesecyclopentadienyl complexes have the general formula(Cp¹R¹ _(m))R³ _(n)(Cp²R² _(p))MX_(q)wherein: Cp¹ and Cp² are the same or different cyclopentadienyl rings;R¹ and R² are each, independently, a halogen or a hydrocarbyl,halocarbyl, hydrocarbyl-substituted organometalloid orhalocarbyl-substituted organometalloid group containing up to about 20carbon atoms; m is 0 to 5; p is 0 to 5; two R¹ and/or R² substituents onadjacent carbon atoms of the cyclopentadienyl ring associated therewithcan be joined together to form a ring containing from 4 to about 20carbon atoms; R³ is a bridging group; n is the number of atoms in thedirect chain between the two ligands and is 0 to 8, preferably 0 to 3; Mis a transition metal having a valence of from 3 to 6, preferably fromgroup 4, 5, or 6 of the periodic table of the elements and is preferablyin its highest oxidation state; each X is a non-cyclopentadienyl ligandand is, independently, a hydrogen, a halogen or a hydrocarbyl,oxyhydrocarbyl, halocarbyl, hydrocarbyl-substituted organometalloid,oxyhydrocarbyl-substituted organometalloid or halocarbyl-substitutedorganometalloid group containing up to about 20 carbon atoms; and q isequal to the valence of M minus 2.

(2) Monocyclopentadienyl complexes which have only one Cp ring system asa ligand. The Cp ligand forms a half-sandwich complex with the metal andcan be free to rotate (unbridged) or locked into a rigid configurationthrough a bridging group to a heteroatom-containing ligand. The Cp ringligand can be unsubstituted, substituted, or a derivative thereof suchas a heterocyclic ring system which may be substituted, and thesubstitutions can be fused to form other saturated or unsaturated ringssystems such as tetrahydroindenyl, indenyl, or fluorenyl ring systems.The heteroatom containing ligand is bound to both the metal andoptionally to the Cp ligand through the bridging group. The heteroatomitself is an atom with a coordination number of three from Group 15 or acoordination number of two from group 16 of the periodic table of theelements. These mono-cyclopentadienyl complexes have the general formula(Cp¹R¹ _(m))R³ _(n)(Y_(r)R²)MX_(s)wherein: each R¹ is independently, a halogen or a hydrocarbyl,halocarbyl, hydrocarbyl-substituted organometalloid orhalocarbyl-substituted organometalloid group containing up to about 20carbon atoms, “m” is 0 to 5, and two R¹ substituents on adjacent carbonatoms of the cyclopentadienyl ring associated there with can be joinedtogether to form a ring containing from 4 to about 20 carbon atoms; R³is a bridging group; “n” is 0 to 3; M is a transition metal having avalence of from 3 to 6, preferably from group 4, 5, or 6 of the periodictable of the elements and is preferably in its highest oxidation state;Y is a heteroatom containing group in which the heteroatom is an elementwith a coordination number of three from Group 15 or a coordinationnumber of two from group 16, preferably nitrogen, phosphorous, oxygen,or sulfur; R² is a radical selected from a group consisting of C₁ to C₂₀hydrocarbon radicals, substituted C₁ to C₂₀ hydrocarbon radicals,wherein one or more hydrogen atoms is replaced with a halogen atom, andwhen Y is three coordinate and unbridged there may be two R² groups on Yeach independently a radical selected from the group consisting of C₁ toC₂₀ hydrocarbon radicals, substituted C₁ to C₂₀ hydrocarbon radicals,wherein one or more hydrogen atoms is replaced with a halogen atom, andeach X is a non-cyclopentadienyl ligand and is, independently, ahydrogen, a halogen or a hydrocarbyl, oxyhydrocarbyl, halocarbyl,hydrocarbyl-substituted organometalloid, oxyhydrocarbyl-substitutedorganometalloid or halocarbyl-substituted organometalloid groupcontaining up to about 20 carbon atoms, “s” is equal to the valence of Mminus 2.

Examples of biscyclopentadienyl metallocenes of the type described ingroup (1) above for producing the mVLDPE polymers of the invention aredisclosed in U.S. Pat. Nos. 5,324,800; 5,198,401; 5,278,119; 5,387,568;5,120,867; 5,017,714; 4,871,705; 4,542,199; 4,752,597; 5,132,262;5,391,629; 5,243,001; 5,278,264; 5,296,434; and 5,304,614.

Illustrative, but not limiting, examples of suitable biscyclopentadienylmetallocenes of the type described in group (1) above are the racemicisomers of:

μ-(CH₃)₂Si(indenyl)₂M(Cl)₂;

μ-(CH₃)₂Si(indenyl)₂M(CH₃)₂;

μ-(CH₃)₂Si(tetrahydroindenyl)₂M(Cl)₂;

μ-(CH₃)₂Si(tetrahydroindenyl)₂M(CH₃)₂;

μ-(CH₃)₂Si(indenyl)₂M(CH₂CH₃)₂; and

μ-(C₆H₅)₂C(indenyl)₂M(CH₃)₂;

wherein M is Zr or Hf.

Examples of suitable unsymmetrical cyclopentadienyl metallocenes of thetype described in group (1) above are disclosed in U.S. Pat. Nos.4,892,851; 5,334,677; 5,416,228; and 5,449,651; and in the publicationJ. Am. Chem. Soc. 1988, 110, 6255.

Illustrative, but not limiting, examples of unsymmetricalcyclopentadienyl metallocenes of the type described in group (1) aboveare:

μ-(C₆H₅)₂C(cyclopentadienyl)(fluorenyl)M(R)₂;

μ-(C₆H₅)₂C(3-methylcyclopentadienyl)(fluorenyl)M(R)₂;

μ-(CH₃)₂C(cyclopentadienyl)(fluorenyl)M(R)₂;

μ-(C₆H₅)₂C(cyclopentadienyl)(2-methylindenyl)M(CH₃)₂;

μ-(C₆H₅)₂C(3-methylcyclopentadienyl)(2-methylindenyl)M(Cl)₂;

μ-(C₆H₅)₂C(cyclopentadienyl)(2,7-dimethylfluorenyl)M(R)₂; and

μ-(CH₃)₂C(cyclopentadienyl)(2,7-dimethylfluorenyl)M(R)₂;

wherein M is Zr or Hf, and R is C₁ or CH₃.

Examples of suitable monocyclopentadienyl metallocenes of the typedescribed in group (2) above are disclosed in U.S. Pat. Nos. 5,026,798;5,057,475; 5,350,723; 5,264,405; 5,055,438; and in WO 96/002244.

Illustrative, but not limiting, examples of monocyclopentadienylmetallocenes of the type described in group (2) above are:

μ-(CH₃)₂Si(cyclopentadienyl)(1-adamantylamido)M(R)₂;

μ-(CH₃)₂Si(3-tertbutylcyclopentadienyl)(1-adamantylamido)M(R)₂;

μ-(CH₂(tetramethylcyclopentadienyl)(1-adamantylamido)M(R)₂;

μ-(CH₃)₂Si(tetramethylcyclopentadienyl)(1-adamantylamido)M(R)₂;

μ-(CH₃)₂C(tetramethylcyclopentadienyl)(1-adamantylamido)M(R)₂;

μ-(CH₃)₂Si(tetramethylcyclopentadienyl)(1-tertbutylamido)M(R)₂;

μ-(CH₃)₂Si(fluorenyl)(1-tertbutylamido)M(R)₂;

μ-(CH₃)₂Si(tetramethylcyclopentadienyl)(1-cyclododecylamido)M(R)₂; and

μ-(C₆H₅)₂C(tetramethylcyclopentadienyl)(1-cyclododecylamido)M(R)₂;

wherein M is Ti, Zr or Hf, and R is C₁ or CH₃.

Other organometallic complexes that are useful catalysts are those withdiimido ligand systems, such as are described in WO 96/23010. Otherreferences describing suitable organometallic complexes includeOrganometallics, 1999, 2046; PCT publications WO 99/14250, WO 98/50392,WO 98/41529, WO 98/40420, WO 98/40374, WO 98/47933; and Europeanpublications EP 0 881 233 and EP 0 890 581.

In particular embodiments, the metallocene compound is abis(cyclopentadienyl)metal dihalide, a bis(cyclopentadienyl)metalhydridohalide, a bis(cyclopentadienyl)metal monoalkyl monohalide, abis(cyclopentadienyl) metal dialkyl, or a bis(indenyl)metal dihalides,wherein the metal is zirconium or hafnium, halide groups are preferablychlorine, and the alkyl groups are C₁–C₆ alkyls. Illustrative, butnon-limiting examples of such metallocenes include:

bis(indenyl)zirconium dichloride;

bis(indenyl)zirconium dibromide;

bis(indenyl)zirconium bis(p-toluenesulfonate);

bis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;

bis(fluorenyl)zirconium dichloride;

ethylene-bis(indenyl)zirconium dichloride;

ethylene-bis(indenyl)zirconium dibromide;

ethylene-bis(indenyl)dimethyl zirconium;

ethylene-bis(indenyl)diphenyl zirconium;

ethylene-bis(indenyl)methyl zirconium monochloride;

ethylene-bis(indenyl)zirconium bis(methanesulfonate);

ethylene-bis(indenyl)zirconium bis(p-toluenesulfonate);

ethylene-bis(indenyl)zirconium bis(trifluoromethanesulfonate);

ethylene-bis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;

isopropylidene(cyclopentadienyl-fluorenyl)zirconium dichloride;

isopropylidene(cyclopentadienyl-methylcyclopentadienyl) zirconiumdichloride;

dimethylsilyl-bis(cyclopentadienyl)zirconium dichloride;

dimethylsilyl-bis(methylcyclopentadienyl)zirconium dichloride;

dimethylsilyl-bis(dimethylcyclopentadienyl)zirconium dichloride;

dimethylsilyl-bis(trimethylcyclopentadienyl)zirconium dichloride;

dimethylsilyl-bis(indenyl)zirconium dichloride;

dimethylsilyl-bis(indenyl)zirconium bis(trifluoromethanesulfonate);

dimethylsilyl-bis(4,5,6,7-tetrahydroindenyl)zirconium dichloride;

dimethylsilyl(cyclopentadienyl-fluorenyl)zirconium dichloride;

diphenylsilyl-bis(indenyl)zirconium dichloride;

methylphenylsilyl-bis(indenyl)zirconium dichloride;

bis(cyclopentadienyl)zirconium dichloride;

bis(cyclopentadienyl)zirconium dibromide;

bis(cyclopentadienyl)methylzirconium monochloride;

bis(cyclopentadienyl)ethylzirconium monochloride;

bis(cyclopentadienyl)cyclohexylzirconium monochloride;

bis(cyclopentadienyl)phenylzirconium monochloride;

bis(cyclopentadienyl)benzylzirconium monochloride;

bis(cyclopentadienyl)zirconium monochloride monohydride;

bis(cyclopentadienyl)methylzirconium monohydride;

bis(cyclopentadienyl)dimethylzirconium;

bis(cyclopentadienyl)diphenylzirconium;

bis(cyclopentadienyl)dibenzylzirconium;

bis(cyclopentadienyl)methyoxyzirconium chloride;

bis(cyclopentadienyl)ethoxyzirconium chloride;

bis(cyclopentadienyl)zirconium bis(methanesulfonate);

bis(cyclopentadienyl)zirconium bis(p-toluenesulfonate);

bis(cyclopentadienyl)zirconium bis(trifluoromethanesulfonate);

bis(methylcyclopentadienyl)zirconium dichloride;

bis(dimethylcyclopentadienyl)zirconium dichloride;

bis(dimethylcyclopentadienyl)ethoxyzirconium chloride;

bis(dimethylcyclopentadienyl)zirconium bis(trifluoromethanesulfonate);

bis(ethylcyclopentadienyl)zirconium dichloride;

bis(methylethylcyclopentadienyl)zirconium dichloride;

bis(propylcyclopentadienyl)zirconium dichloride;

bis(methylpropylcyclopentadienyl)zirconium dichloride;

bis(butylcyclopentadienyl)zirconium dichloride;bis(methylbutylcyclopentadienyl)zirconium dichloride;

bis(methylbutylcyclopentadienyl)zirconium bis(methanesulfonate);

bis(trimethylcyclopentadienyl)zirconium dichloride;

bis(tetramethylcyclopentadienyl)zirconium dichloride;

bis(pentamethylcyclopentadienyl)zirconium dichloride;

bis(hexylcyclopentadienyl)zirconium dichloride;

bis(trimethylsilylcyclopentadienyl)zirconium dichloride;

bis(cyclopentadienyl)zirconium dichloride;

bis(cyclopentadienyl)hafnium dichloride;

bis(cyclopentadienyl)zirconium dimethyl;

bis(cyclopentadienyl)hafnium dimethyl;

bis(cyclopentadienyl)zirconium hydridochloride;

bis(cyclopentadienyl)hafnium hydridochloride;

bis(n-butylcyclopentadienyl)zirconium dichloride;

bis(n-butylcyclopentadienyl)hafnium dichloride;

bis(n-butylcyclopentadienyl)zirconium dimethyl;

bis(n-butylcyclopentadienyl)hafnium dimethyl;

bis(n-butylcyclopentadienyl)zirconium hydridochloride;

bis(n-butylcyclopentadienyl)hafnium hydridochloride;

bis(pentamethylcyclopentadienyl)zirconium dichloride;

bis(pentamethylcyclopentadienyl)hafnium dichloride;

bis(n-butylcyclopentadienyl)zirconium dichloride;

cyclopentadienylzirconium trichloride;

bis(indenyl)zirconium dichloride;

bis(4,5,6,7-tetrahydro-1-indenyl)zirconium dichloride; and

ethylene-[bis(4,5,6,7-tetrahydro-1-indenyl)] zirconium dichloride.

A solution of the metallocene compound and an alumoxane activator isprepared, in an aromatic solvent, such as benzene, toluene or ethylbenzene. Alumoxanes are oligomeric aluminum compounds represented by thegeneral formula (R—Al—O)_(n), which is a cyclic compound, orR(R—Al—O)_(n)AlR₂, which is a linear compound. In these formulae, each Ror R′ is a C₁ to C₈ alkyl radical, for example, methyl, ethyl, propyl,butyl or pentyl, and “n” is an integer from 1 to about 50. Mostpreferably, R is methyl and “n” is at least 4, i.e., methylalumoxane(MAO). Alumoxanes can be prepared by various procedures known in theart. For example, an aluminum alkyl may be treated with water dissolvedin an inert organic solvent, or it may be contacted with a hydratedsalt, such as hydrated copper or iron sulfate suspended in an inertorganic solvent, to yield an alumoxane. Examples of alumoxanepreparation can be found in U.S. Pat. Nos. 5,093,295 and 5,902,766, andreferences cited therein. Generally, however prepared, the reaction ofan aluminum alkyl with a limited amount of water yields a complexmixture alumoxanes. Further characterization of MAO is described in D.Cam and E. Albizzati, Makromol. Chem. 191, 1641–1647 (1990). MAO is alsoavailable from various commercial sources, typically as a 30 wt %solution in toluene. In one embodiment, the amount of aluminum providedby the alumoxane is sufficient to provide an aluminum to metallocenetransition metal mol/mol ratio of from 50:1 to 500:1, or from 75:1 to300:1, or from 85:1 to 200:1, or from 90:1 to 110:1. Typically, thealumoxane and metallocene compound are mixed together at a temperatureof 20 to 80° C. for 0.1 to 6.0 hours.

To prepare the bimetallic catalyst, the dried, supported non-metallocenetransition metal catalyst is re-slurried in a light aliphatichydrocarbon that can be the same or different from the hydrocarbon usedin preparing the silica slurry. The hydrocarbon can have a boiling pointof less than 90° C., such as −50 to 89° C., −25 to 70° C., −5 to 50° C.,or 10 to 35° C. Suitable hydrocarbons include, for example, isopentane,hexane, isohexane, n-heptane, octane, nonane, decane, or cyclohexane.

The slurry of the non-metallocene transition metal catalyst is contactedwith the metallocene/alumoxane solution. Preferably, the volume of themetallocene/alumoxane solution does not exceed the total pore volume ofthe support. Typically, the volume ratio of the light aliphatichydrocarbon used for the non-metallocene transition metal catalystslurry to the aromatic solvent used for the metallocene compoundsolution is from 0.5:1 to 20:1, or from 1:1 to 15:1, or from 2:1 to10:1, or from 2.5:1 to 8:1.

The contact product thus obtained is then dried, typically at atemperature of 40–60° C., to obtain the supported bimetallic catalyst.

The bimetallic catalyst can be used to produce polyolefin homopolymersand copolymers having bimodal distributions of molecular weight,comonomer composition, or both. These catalysts can be used in a varietyof polymerization reactors, such as fluidized bed reactors, autoclaves,and slurry reactors.

6. EXAMPLES Example 1

This example shows that the activity of the supported non-metallocenetransition metal catalyst is increased when the support material used toprepare the catalyst is dehydrated at a higher temperature than isconventionally used. Two samples of Davison 955 silica were dehydrated,one at a temperature of 600° C. (Sample 1A) and one at a temperature of850° C. (Sample 1B). The dehydrated silicas were then treated withdibutylmagnesium (0.72 mmol/g silica), butanol, and titaniumtetrachloride as described above, to yield a supported non-metallocenetransition metal catalyst. This catalyst was then used in a laboratoryslurry reactor to polymerize ethylene, and the catalyst activity wasdetermined for each sample. Sample 1A (using 600° C. dehydrated silica)showed an activity of 3900 grams polyethylene per gram catalyst perhour, and Sample 1B (using 850° C. dehydrated silica) showed an activityof 4960 grams polyethylene per gram catalyst per hour.

Example 2

Two non-metallocene transition metal catalysts were prepared. Samples ofDavison 955 silica were dehydrated under nitrogen flow for 4 hours at600° C. (Sample 2A) and at 800° C. (Sample 2B). Each sample was thentreated as follows. 4.00 g of the dehydrated silica was placed into aSchlenk flask with 100 mL hexane. The flask was placed into an oil bathat about 50° C., with stirring. Dibutylmagnesium (2.88 mmol) was addedvia syringe to the stirred slurry at about 50° C. and the slurry wasstirred at this temperature for 1 hour. 2.96 mmol of n-butanol was addedvia syringe to the stirred mixture at about 50° C. and the mixture wasstirred at this temperature for 1 hour. Finally, 1.728 mmol of TiCl₄ wasadded via syringe to the mixture at about 50° C. and stirring continuedfor 1 hour. Then, the liquid phase was removed under nitrogen flow atabout 50° C. to yield a free-flowing powder.

Ethylene/1-hexene copolymers were prepared using the two samples. A 2.0L stainless steel autoclave was charged with hexane (750 mL) and1-hexene (40 mL) under a slow nitrogen purge and then 2.0 mmol oftrimethylaluminum (TMA) was added. The reactor vent was closed, thestirring was increased to 1000 rpm, and the temperature was increased to95° C. The internal pressure was raised 6.0 psi (41 kPa) with hydrogenand then ethylene was introduced to maintain the total pressure at 270psig (1.9 MPa). Then, the temperature was decreased to 85° C., 20.3 mgof the catalyst was introduced into the reactor with ethyleneover-pressure, and the temperature was increased and held at 95° C. Thepolymerization reaction was carried out for 1 hour and then the ethylenesupply was stopped. The reactor was cooled to ambient temperature andthe polyethylene was collected.

The catalyst prepared from 600° C. dehydrated silica (Sample 2A) had anactivity of 3620 grams polyethylene per gram catalyst per hour, and thecatalyst prepared from 800° C. dehydrated silica (Sample 2B) had anactivity of 4610 grams polyethylene per gram catalyst per hour.

Example 3

Two samples of bimetallic catalysts were prepared. First,non-metallocene catalysts were prepared using 600° C. dehydrated silica(Sample 3A) and 800° C. dehydrated silica (Sample 3B) as in Example 2.Each sample was then treated as follows. The dried non-metallocenecatalyst was reslurried in hexane (5 mL per gram of catalyst) at ambienttemperature, with stirring. To this stirred slurry was slowly added asolution of the reaction product of 30 wt % MAO in toluene (6.8 mmolAl/g non-metallocene catalyst) and bis(n-butylcyclopentadienyl)zirconiumdichloride (Al/Zr molar ratio 100:1). The dark brown mixture was stirredat ambient temperature for 1 hour and then heated to about 45° C. Theliquid phase was then removed under nitrogen flow to yield afree-flowing brown powder.

The two bimetallic catalyst samples were then used to polymerizeethylene/1-hexene as described in Example 2. The bimetallic catalystprepared with 600° C. dehydrated silica (Sample 3A) had an activity of1850 grams polyethylene per gram bimetallic catalyst per hour, and thebimetallic catalyst prepared with 800° C. dehydrated silica (Sample 3B)had an activity of 2970 grams polyethylene per gram bimetallic catalystper hour.

Example 4

The bimetallic catalysts prepared according to Example 3 were used topolymerize ethylene/1-hexene in a pilot scale fluidized bed reactor.Example 4A in Table 1 shows the reactor conditions and results for thecatalyst of Sample 3A, and Example 4B shows the reactor conditions andresults for the catalyst Sample 3B.

TABLE 1 Example 4A (comparative) Example 4B Reactor Temperature (° F.(°C.)) 203 (95)  203 (95)  H₂/C₂ gas mole ratio 0.011 0.011 C₆/C₂ gas moleratio 0.007 0.008 C₂ partial pressure (psi(MPa)) 156.9 (1.082) 158.5(1.093) H₂O (ppm¹) 7.2 21.0 TMA (ppm¹) 100 100 Productivity (g/g) 18204040 Flow Index I_(21.6) (dg/min)² 6.6 6.4 ¹parts per million partsethylene, by weight ²measured according to ASTM D-1238, condition F(21.6 kg load, 190° C.)

The results of Examples 1–4 are summarized in Table 2. In each example,the “A” sample is a comparative example, where the silica was dehydratedat 600° C., and the “B” sample is the inventive example. Note that theactivities in different rows are not directly comparable because ofdifferences in catalyst, polymerization processes, etc. Within a row,however, the change in activity (% increase) shows the unexpectedadvantages of the inventive methods and compositions.

TABLE 2 Activity (“A” sample)¹ Activity (“B” sample) (gPE/g cat/hr)(gPE/g cat/hr) % increase Example 1 3900 4960 27% Example 2 3620 461027% Example 3 1850 2970 61% Example 4 1820 4040 122% ¹comparativeexamples

Example 5

Supported non-metallocene catalysts based on TiCl₄ were prepared asdescribed in Example 2, except that samples of silica were dehydrated atvarious temperatures from 600° C. to 830° C. Ethylene/1-hexenecopolymers were prepared using the titanium catalysts as follows. A 2.0L stainless steel autoclave was charged with isobutane (800 mL) and1-hexene (20 mL) under a slow nitrogen purge and then 1.86 mmol oftrimethylaluminum (TMA) was added. The reactor vent was closed, thestirring was increased to 1000 rpm, and the temperature was increased to85° C. Ethylene and 75 mmol hydrogen were added to provide a totalpressure of 325 psig (2.24 MPa). 100 mg of the catalyst was introducedinto the reactor with ethylene over-pressure, and the temperature washeld at 85° C. The polymerization reaction was carried out for 40minutes and then the ethylene supply was stopped. The reactor was cooledto ambient temperature and the polyethylene was collected. For eachdehydration temperature, two samples were prepared and run. Table 3shows the activity results at each temperature.

TABLE 3 Si dehydration Activity, Run 1 Activity, Run 2 Activity, averagetemperature (° C.) (gPE/g cat/hr) (gPE/g cat/hr) (gPE/g cat/hr) 600 12751425 1350 680 1440 1395 1417 730 2025 2175 2017 780 2055 2010 2032 8301680 1530 1605 FIG. 1 shows the average activity versus dehydrationtemperature graphically (filled diamonds, left axis).

Example 6

In this Example, the non-metallocene catalysts of Example 5 were used toprepare bimetallic catalysts, according to Example 3. Polymerization ofethylene/1-hexene was then carried out as follows. A 2.0 L stainlesssteel autoclave was charged with n-hexane (700 mL), 1-hexene (40 mL) andwater (14 μL) under a slow nitrogen purge and then 2.0 mL oftrimethylaluminum (TMA) was added. The reactor vent was closed, thestirring was increased to 1000 rpm, and the temperature was increased to95° C. Ethylene and 4 psig (28 kPa) hydrogen were added to provide atotal pressure of 205 psig (1.41 MPa). 30 mg of the bimetallic catalystwas introduced into the reactor with ethylene over-pressure, and thetemperature was held at 95° C. The polymerization reaction was carriedout for 60 minutes and then the ethylene supply was stopped. The reactorwas cooled to ambient temperature and the polyethylene was collected.For each dehydration temperature, at least two samples were prepared andrun. Table 4 shows the activity results at each temperature.

TABLE 4 Si Activity dehydration Run 1 Activity Activity Activity,temperature (gPE/g Run 2 Run 3 average (° C.) cat/hr) (gPE/g cat/hr)(gPE/g cat/hr) (gPE/g cat/hr) 600 2761 2304 * 2532 680 3416 2399 34543090 730 5250 4137 4810 4732 780 5674 4682 * 5178 830 5137 4953 * 5045 *no data

FIG. 1 shows the average activity versus dehydration temperaturegraphically (filled squares, right axis), along with the non-metallocenetransition metal catalyst data for comparison. As is clear from theFigure, the activity of both the non-metallocene transition metalcatalyst and the bimetallic catalyst is surprisingly enhanced usingsilica dehydrated at temperatures greater than 600° C.

All patents, test procedures, and other documents cited herein,including priority documents, are fully incorporated by reference to theextent such disclosure is not inconsistent with this invention and forall jurisdictions in which such incorporation is permitted.

1. A process for preparing a bimetallic catalyst, the processcomprising: (a) providing a supported non-metallocene catalyst by: (i)dehydrating a particulate support material at a temperature of greaterthan 600° C.; (ii) preparing a slurry of the dehydrated support in anon-polar hydrocarbon; (iii) contacting the slurry of (ii) with anorganomagnesium compound RMgR′, where R and R′ are the same or differentC₂–C₁₂ alkyl groups; (iv) contacting the slurry of (iii) with anon-metallocene compound of a Group 4 or Group 5 transition metal,wherein the non-metallocene transition metal compound is used in anamount to provide from 0.3 to 1.5 moles of the Group 4 or 5 transitionmetal per mole of magnesium provided by the organomagnesium compound;and (v) drying the product of (iv) to obtain a supported non-metallocenecatalyst; (b) contacting a slurry of the supported non-metallocenecatalyst in a non-polar hydrocarbon with a solution of a metallocenecompound and a C₁–C₈ alkyl alumoxane in an aromatic solvent; and (c)drying the product of (b) to obtain a supported bimetallic catalyst. 2.The process of claim 1, wherein the support material is silica.
 3. Theprocess of claim 1, wherein the support material is dehydrated at atemperature of from 650° C. to 900° C.
 4. The process of claim 1,wherein the support material is dehydrated at a temperature of from 700°C. to 850° C.
 5. The process of claim 1, wherein the support material isdehydrated at a temperature of from 750° C. to 800° C.
 6. The process ofclaim 1, wherein the non-polar hydrocarbon in (a) is selected from thegroup consisting of C₄–C₁₀ linear or branched alkanes, cycloalkanes andaromatics.
 7. The process of claim 1, wherein the organomagnesiumcompound is dibutylmagnesium.
 8. The process of claim 1, wherein theorganomagnesium compound is used in an amount of from 0.2 mmol to 2 mmolorganomagnesium compound per gram of dehydrated support material.
 9. Theprocess of claim 1, further comprising before step (iv), contacting theslurry of (iii) with an electron donor.
 10. The process of claim 9,wherein the electron donor comprises an alcohol R″OH, where R″ is aC₁–C₁₂ alkyl group.
 11. The process of claim 10, wherein the alcohol isn-butanol.
 12. The process of claim 10, wherein the alcohol is used inan amount of 0.2 to 1.5 moles per mole of magnesium provided by theorganomagnesium compound.
 13. The process of claim 1, wherein the Group4 or 5 transition metal is titanium or vanadium.
 14. The process ofclaim 1, wherein the non-metallocene transition metal compound is atitanium halide, a titanium oxyhalide, a titanium alkoxyhalide, avanadium halide, a vanadium oxyhalide or a vanadium alkoxyhalide. 15.The process of claim 1, wherein the metallocene compound is asubstituted, unbridged bis-cyclopentadienyl compound.
 16. The process ofclaim 1, wherein step (b) is carried out at a temperature of less than90° C.
 17. A process for preparing a bimetallic catalyst, the processcomprising: (a) providing a supported non-metallocene catalyst by: (i)dehydrating a particulate support material at a temperature of from 650°C. to 900° C.; (ii) preparing a slurry of the dehydrated support in anon-polar hydrocarbon; (iii) contacting the slurry of (ii) with anorganomagnesium compound RMgR′, where R and R′ are the same or differentC₂–C₁₂, alkyl groups; (iv) contacting the slurry of (iii) with anon-metallocene compound of a Group 4 or Group 5 transition metal; and(v) drying the product of (iv) to obtain a supported non-metallocenecatalyst; (b) contacting a slurry of the supported non-metallocenecatalyst in a non-polar hydrocarbon with a solution of a metallocenecompound and a C₁–C₈ alkyl alumoxane in an aromatic solvent; and (c)drying the product of (b) to obtain a supported bimetallic catalyst. 18.The process of claim 17, wherein the support material is silica.
 19. Theprocess of claim 17, wherein the support material is dehydrated at atemperature of from 700° C. to 850° C.
 20. The process of claim 17,wherein the support material is dehydrated at a temperature of from 750°C. to 800° C.
 21. The process of claim 17, wherein the non-polarhydrocarbon in (a) is selected from the group consisting of C₄–C₁₀linear or branched alkanes, cycloalkanes and aromatics.
 22. The processof claim 17, wherein the organomagnesium compound is dibutylmagnesium.23. The process of claim 17, wherein the organomagnesium compound isused in an amount of from 0.2 mmol to 2 mmol organomagnesium compoundper gram of dehydrated support material.
 24. The process of claim 17,further comprising before step (iv), contacting the slurry of (iii) withan electron donor.
 25. The process of claim 24, wherein the electrondonor comprises an alcohol R″OH, where R″ is a C₁–C₁₂ alkyl group. 26.The process of claim 25, wherein the alcohol is n-butanol.
 27. Theprocess of claim 25, wherein the alcohol is used in an amount of 0.2 to1.5 moles per mole of magnesium provided by the organomagnesiumcompound.
 28. The process of claim 17, wherein the Group 4 or 5transition metal is titanium or vanadium.
 29. The process of claim 17,wherein the non-metallocene transition metal compound is a titaniumhalide, a titanium oxyhalide, a titanium alkoxyhalide, a vanadiumhalide, a vanadium oxyhalide or a vanadium alkoxyhalide.
 30. The processof claim 17, wherein the non-metallocene transition metal compound isused in an amount to provide from 0.3 to 1.5 moles of the Group 4 or 5transition metal per mole of magnesium provided by the organomagnesiumcompound.
 31. The process of claim 17, wherein the metallocene compoundis a substituted, unbridged bis-cyclopentadienyl compound.
 32. Theprocess of claim 17, wherein step (b) is carried out at a temperature ofless than 90° C.